While some pundits criticised Chelsea's tactical defensive blanket in the Vicente Calderon, suggesting they should have gone to score a vital away goal, the record books suggest the performance tilted the tie firmly in their favour.

In the 22 years of the competition, 25 teams have got a goalless draw in the away leg, with 18 of those going through.

Since the adoption of the last 16 stage in 2003-04, the success rate of teams that managed a goalless away draw has gone up, to 80 per cent, with 12 out of 15 progressing.

Of course, Chelsea were themselves one of the exceptions, thanks more to Norwegian referee Tom Henning Ovrebo than Andres Iniesta's last-gasp strike for Barcelona in the 2009 semi-final.

But that history, along with the fact they have never lost a second leg tie at home, gives Chelsea confidence.

On the other hand, the big problem is that, as Mourinho's men proved in Madrid and on Merseyside, possession is not exactly nine-tenths of the football law.

Through the tournament, Chelsea have averaged 50.54 per cent of the ball. And that included games against poor sides such as Steaua Bucharest and Schalke.

Atletico though, despite dominating possession in the first leg, in a game alien to their customary nature, have averaged just 38.3 per cent.

That leaves a slack of 11.3 per cent, which Atletico will doubtless oblige the hosts to pick up, forcing Chelsea to ''make'' the game rather than play in the counter-attacking style they clearly prefer.

''They're in the semi-finals of the Champions League and they need two victories to be champions in Spain, so I don't think it's fair to analyse them in such a way. I think it's fair to say they're a good team, a very good team.

''In this moment, this is a clean result. It's 0-0 so that means it has possibilities for both teams, probably the same possibilities.

''We play at home, but a draw with goals is good for them and not us. So we cannot really say which one has the advantage. Everything is very balanced. But we have to enjoy it, really. The players, too.

''There are some matches that are special. The match every player wants to play is the Champions League final, but after that game it's the second leg of the Champions League semi-final.

''So we have to enjoy it. After the game, let's see if we go to Lisbon or not. I will go for sure in the summer anyway. But let's see if we can go together!''

Atletico midfielder Tiago, part of Mourinho's first title-winning Chelsea side in 2004-05 and in the team that lost at Anfield to the Luis Garcia ''ghost goal'', predicted: ''We know it'll be very difficult because they don't leave any spaces.

''But we need to find a solution for that. It'll be quite a difficult game for both sides. It's a semi-final of the Champions League, so it won't be easy.

''We know Chelsea will start strongly. They're well organised and will try and take advantage of set-pieces: corners, free-kicks.

''So we'll have to do the same, and take advantage of the possession we have. We have similar virtues to them, and we'll just try and prove stronger than them in the end.''